The invention relates to a disc brake, preferably to a pneumatically actuated disc brake for utility vehicles. The disc brake includes a brake caliper enclosing a brake disc with brake pads fixed to brake pad carrier plates arranged on both sides of the brake disc. A rotary-mounted brake lever and a brake application device are provided, which are fitted laterally beside the brake disc. The brake application device is equipped with at least two pistons situated transversely in relation to the brake disc and carried in a bridge, the end faces of the pistons being assigned to the opposing brake pad carrier plate and come into contact with the brake pad carrier plate.
The disc brake in question is further equipped with a brake cylinder, which in a braking sequence transmits a force to the brake lever. Carried in the bridge are threaded spindles, which at their ends assigned to the brake disc carry the pistons. These threaded spindles serve to adjust the lifting clearance of the brake, so as to compensate for brake pad wear.
In the case of the known disc brake, it has proved advantageous if the pistons in a braking sequence bear against the opposing face of the brake pad carrier plate with the greatest possible frictional force, since tangential forces are then absorbed, thereby relieving the bridge of bending stresses through such contact between the pistons and the opposing faces of the brake pad carrier plates. The smooth contact faces, however, mean that such relief is relatively slight, making the reduction achieved in the bending stresses acting on the bridge negligible.
The object of the invention is to design a disc brake such that, in the process of braking, the bending forces acting on the bridge are significantly reduced, while nevertheless ensuring that the brake pad is supported on the brake pad carrier plate, due to the tangentially acting forces.
According to the invention, the end faces of the pistons and at least the contact faces of the opposing brake pad carrier plate are provided with positively intermeshing (form-fitting) profiles, such that each brake pad is displaceable in a peripheral direction, at least in full-load braking. Such “profiles” might also be referred to as ramps. The profiles in the end faces of the pistons and the profiles in the opposing face of the brake pad carrier plate are of complementary design. In addition, they are designed, in their orientation and inclination, so that tangential forces are, to a desired extent, absorbed by the pistons, and that the peripheral displacement of each brake pad is still sufficient to allow it to bear against the brake pad carrier plate horn. The profiles are, moreover, designed so as to limit the maximum tangential force to be absorbed by the pistons.
The solution according to the invention further ensures that a feed movement of the brake pad in its actuating direction is performed due to the peripheral displacement of the brake pad in the profiles or in the ramps. In this way a limited use is made of a self-energizing (intensifying) effect, so as to compensate for a part of the expansion of the brake caliper.
In order to preclude rattling noises and the like from occurring, the end faces of the pistons and the contact faces of the opposing brake pad carrier plate intermesh without any play. It is particularly advantageous here, not least with a view to manufacturing precision, if the intermeshing profiles can be geometrically defined. Thus, in a preferred embodiment, the profiles of the end faces of the pistons and the profiles of the corresponding areas of the opposing face of the brake pad carrier plate consist of grooves and lands engaging in the grooves, which are arranged constantly alternating with one another.
For example, the grooves may have triangular-shaped cross sections. The cross sections here can then be uniform or irregular. The exact design shape is determined by the coefficient of friction of the brake pad. The angles of inclination may be between 15° and 40°, according to the coefficient of friction of the brake pad. These angles advantageously lie between 20° and 30°, assuming a coefficient of friction of the brake pad of 0.375.
The disc brake is appropriately designed so that the possible displacement travel of the brake pad in a peripheral direction is preferably limited, so that the feed travel of the brake pad obtained over the profiles cannot exceed the size of the lifting clearance. This ensures that the brake is perfectly releasable, regardless of the friction ratios on the brake pad and the profiles.